Question: A box contains $6$ red balls, $4$ green balls, and $9$ blue balls. If a ball is randomly chosen, what is the probability that it is not red?
Answer: There are $6 + 4 + 9 = 19$ balls in the box. There are $6$ red balls. That means $19 - 6 = 13$ are not red. The probability is $ \frac{13}{19}$.